Knowledge Article: Space Management for PostgreSQL Databases
Effective space management is critical for maintaining database performance and availability. This guide explains how to monitor disk space using your daily morning checks or internal reporting tools and the process for requesting disk space expansion through a SNOW ticket.
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Monitoring Disk Space
1. Using Morning Checks or Internal Reporting Tools
Morning checks involve systematically reviewing critical database metrics, including disk space usage, to proactively identify potential issues.
Steps to Monitor Disk Space:
1. Access Reporting Tool: Log in to your internal monitoring or reporting tool used for database space metrics.
2. Review File System Usage:
Check the PostgreSQL data directories (e.g., /var/lib/pgsql/data or custom paths).
Focus on the key filesystems hosting PostgreSQL data, WAL (Write-Ahead Logs), and backup directories.
3. Analyze Tablespace Usage: Run the following SQL queries in the PostgreSQL database to monitor tablespace utilization:
SELECT spcname AS tablespace,
pg_size_pretty(pg_tablespace_size(spcname)) AS size
FROM pg_tablespace
ORDER BY pg_tablespace_size(spcname) DESC;
This will display the size of each tablespace in human-readable format.
4. Identify Critical Thresholds:
If disk usage exceeds 80%, flag it for further action.
Use alert systems in your monitoring tool to warn you when predefined thresholds are breached.
5. WAL Directory Monitoring: Monitor the WAL directory for excessive log file generation:
SELECT pg_current_wal_lsn();
Use internal metrics to estimate the growth trend of WAL files.
2. Generate Reports
Ensure daily reports are distributed to stakeholders. Include:
Total and used disk space by directory.
Tablespace usage trends.
Notifications of any space concerns.
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Requesting Disk Space Increase
When space usage approaches critical levels and proactive cleaning measures are insufficient, initiate a disk space expansion request.
1. Open a SNOW Ticket
Follow the organization's process for creating a ServiceNow (SNOW) ticket to request additional disk space. Include the following details in the ticket:
Subject:
"Request for Disk Space Expansion for PostgreSQL Server"
Details:
Server Name: Mention the hostname or IP address of the affected server.
Filesystem Details:
Filesystem Path: Specify the full path of the directory requiring space (e.g., /data or /pg_wal).
Current Size: Mention the current size and usage percentage.
Requested Increase: Specify the additional space needed (e.g., +50GB or +20%).
Business Impact: Explain why the increase is necessary (e.g., "Critical database operations may be impacted due to lack of space").
Attachments: Attach screenshots or reports from monitoring tools to support the request.
2. Involve the UNIX and VISM Teams
The UNIX team will manage the disk extension, while the VISM team will ensure changes align with enterprise storage policies. Ensure both teams are tagged in the ticket for a streamlined response.
3. Post-Increase Validation
After the space increase is completed:
1. Validate the change using df -h or the internal reporting tool.
2. Verify PostgreSQL is running without errors or warnings related to disk space.
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Best Practices for Space Management
1. Archiving and Cleanup:
Automate WAL file archiving to a secondary storage location.
Remove unused or outdated backups periodically.
2. Tablespace Maintenance:
Reindex large tables to reclaim space.
Use partitioning for better space management.
3. Proactive Alerts:
Set up email or SMS alerts for disk usage exceeding 70% to plan expansions.
4. Capacity Planning:
Forecast disk usage based on database growth trends and plan upgrades in advance.
By following these guidelines, you can ensure optimal space management for PostgreSQL databases, minimizing disruptions and maintaining high performance.
